The present invention generally relates to a novel circuit which can improve the power factor of a power supply when experiencing a light load. Specifically, it relates to a circuit which can achieve a higher power factor even in a light load condition.
In order to reduce the harm caused by harmonics and reactive power, power factor correction technique is widely used in power electronics equipments. A majority of the power factor correction (PFC) circuits can achieve higher power factor (PF) value in heavy load condition, but when the load reduces, the PF value will also decrease accordingly. Normally, for power factor correction circuits which are suitable for a wide input voltage range, the PF value decreases more drastically when the load reduces in the high input voltage terminal. Currently, electrical equipment with higher PF value is required in more occasions in which there is a wide load range. Therefore, techniques required to improve light load power factor for power supply are becoming important.